A method for mapping systems described by light onto circuits using qubits now links photonic and qubit-based approaches to quantum computing. The technique truncates the mathematical description of single-mode optical states, known as Fock space, to dimension N = 2 and N = 4.; enabling representation of operations like phase rotations and beam splitters. A Python compiler called COΦ is also available, translating photonics programs into code for existing quantum computers.

Instructions used in light-based (photonic) quantum computing can now be translated into commands for conventional digital computers using qubits, the basic units of quantum information. This enables simulation on existing hardware of complex behaviours of light, such as those found in Gaussian Boson Sampling. Connecting these separate approaches more easily builds hybrid systems combining advantages of both photonic and qubit technologies. Photonic and qubit-based approaches to quantum computing are bridged by a method representing light systems with qubits; this allows complex behaviours like Gaussian Boson Sampling to be simulated on current digital hardware.

The key is truncating ‘Fock space’, which describes all possible states of photons, imagine it as an inventory list of photon counts, simplifying calculations by focusing only on relevant portions. This truncated information translates into instructions for qubits via OpenQASM, assembly code tailored for quantum computers dictating precise operations. Releasing COΦ, a Python compiler automating translation from photonic programs to qubit commands, creates a strong set of tools for building hybrid quantum systems.

Simulating Quantum Photonics with Expanded Fock Space Dimensions Enables Complex Circuit Construction

This breakthrough crosses a key threshold for simulating complex behaviours like Gaussian Boson Sampling, intractable using infinite dimensional representations but feasible within this truncated framework. By mapping light states onto qubits through controlled simplification of mathematical descriptions known as ‘Fock spaces’, researchers created explicit circuit constructions representing fundamental photonic operations such as phase rotations and beam splitters.

To aid wider adoption, the team released COΦ, an open-source Python compiler available via GitHub that translates programs designed for simulating light into instructions understood by standard qubit-based quantum computers utilising this truncation method. It converts Blackbird quantum optics programmes to OpenQASM circuits allowing broader testing and application of their approach, though demonstrating scalability towards hundreds or thousands of photons remains a challenge needed to outperform classical computers in practical Gaussian Boson Sampling scenarios.

Scalability constraints hinder near term advantage in boson sampling

While successfully demonstrating simulations with four dimensions represents a leap from previous work, the discussion surrounding limitations on scalability feels understated. Despite these acknowledged scaling limits, representing increasingly complex light behaviour with digital circuits offers valuable groundwork for hybrid approaches and supports innovation even within current hardware constraints.

This bridges photonic and digital quantum computing by translating light behaviour into standard instructions empowering researchers to begin refining techniques now. The open-source software tool allows experimentation and refinement relevant to Gaussian Boson Sampling.

Through simplification of how light states are mathematically described using Fock space truncation, the Jagiellonian University and Polish Academy of Sciences team connected photonic systems with digital computers, allowing representation of fundamental actions involving light as instructions for standard quantum circuits utilising qubits, the basic units of quantum information. Above all, this extends beyond theory through COΦ; it enables translation between programs designed for photonics and those executable on existing qubit hardware, facilitating broader testing and application.

This research successfully mapped quantum optical systems onto qubit-based quantum circuits by truncating the mathematical description of single-mode optical states, specifically to dimensions of two and four. This connection allows researchers to simulate how light behaves using standard quantum computer instructions, offering a new way to explore photonic processes digitally. While scalability remains a challenge, this work provides a framework for hybrid approaches within current hardware limitations.

👉 More information
🗞 CO$Φ$ – COmpiling PHotonics into dIgital quantum circuits
✍️ Grzegorz Czelusta, Jakub Mielczarek and Artur Miroszewski (Jagiellonian University); Marcin Markiewicz (Polish Academy of Sciences)
🧠 ArXiv: https://arxiv.org/abs/2610.28349

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